This invention relates to seals for fasteners and the like, and more particularly, to a seal assembly which is self centering and may be preassembled and retained on the fastener to facilitate assembly procedures.
Sealing fasteners against leakage can pose a serious challenge where excessively large clearance holes are involved, typically where there is greater than 1/32" diametral clearance. An oil drain plug is one example of this situation while a pressurized structural assembly is another. It is necessary to assure in these instances that the sealing member accommodates the tolerance range of both the opening to be sealed and the fastener involved in order to avoid a leak path.
This problem is accentuated if it is necessary to keep the fastener in tight engagement, that is, where there is no torque loss over a period of time. This requirement rules out the use of a plain rubber or composition flat washer which relaxes and takes a set over a period of time.
Still other problems inherent in devices of this type are requirements that the sealing device be preassembled with the fastener to facilitate handling and to ensure against inadvertent omission, and from the functional standpoint, the requirement that the sealing device retain its resilience over its intended service life.